The die casting plants in question generally comprise at least one die, consisting of two half-dies, into which the molten metal is injected. The die is kept closed by hydraulic presses for the entire duration of the injection and is opened at the end of the injection for extracting the cooled and solidified piece.
A known device for detecting thermographic images and intended for a metallurgical plant is described, for example, in patent document EP1535034 which relates to a system for controlling technological processes to optimise operating temperatures.
The detecting device comprises a radiation sensor, for example comprising a so-called thermal camera, which is directed at a respective half-die.
When opening the die, the radiation sensor, which is sensitive in particular to infrared radiation, acquires thermological parameters, in particular by acquiring a thermographic image, of a surface of the half-die.
The data acquired is sent to a computerised command and control unit, in communication with the detecting device, by means of corresponding wiring, for subsequent processing.
The detecting device comprises a protective case inside of which is housed the thermal camera which is thus protected from environmental disturbances typical of die casting processes.
The case is provided with a window, closed for example by a germanium lens, through which the thermal camera is capable of acquiring the above-mentioned thermographic images.
The detecting device comprises a shutter or screen of the above-mentioned window to protect it in turn from the ambient disturbances during operation of the plant.
The shutter is movable between a first operating configuration wherein the window is open, that is, thermal camera has a clear field of vision for acquiring the thermographic images, and a second operating position wherein the window is closed and protected.
The detecting device comprises a pneumatic system in communication with the inside of the case to cool the radiation sensor and in communication with the outside of the case, at the window, in order to keep the closing lens clean.
The prior art solutions have some drawbacks.
The pneumatic system comprises a unit for distribution of the air in communication with a source of compressed air and a plurality of pipes for feeding air from the distribution unit to the protective case.
The distribution unit is located outside the protective case and, to prevent excessive pressure losses, the unit must be positioned relatively close to the case and the sensor, approximately within ten meters, thus limiting the possibility of setting up the control system.
The cooling of the radiation sensor is performed by continuously injecting air inside the case with a consequent relatively high consumption of air and a cooling of the sensor which is not entirely optimum.
The pipes for supplying the air to the protective case are positioned outside the case and the distribution unit and are therefore exposed to the environmental disturbances and are therefore particularly subject to faults.
In this context, the main aim of this invention is to obviate the above-mentioned drawbacks.